Victoria researchers help develop map of Milky Way

Click for full size versionA sky map of the Faraday effect
caused by the magnetic fields of the Milky Way. Red and blue
colours indicate regions of the sky where the magnetic field
points toward and away from the observer, respectively.
Image: Max Planck Institute for
Astrophysics.

MEDIA
RELEASE

21 February 2012

Victoria
researchers help develop map of Milky Way

We now
have a new way of viewing the Milky Way, thanks to Victoria
astronomer Melanie Johnston-Hollitt and one of her
undergraduate students.

Dr Johnston-Hollitt and student
Luke Pratley, who is about to begin an Honours degree in
Physics, are part of an international team that has produced
the highest precision map ever of the Milky Way galaxy’s
magnetic field.

The team, led by Niels Oppermann of
Germany’s Max Planck Institute for Astrophysics (MPA),
pooled data from radio astronomy observations to map the
galaxy’s magnetic field.

In 2004, Dr Johnston-Hollitt
produced the first such map of the Milky Way with Dr
Christopher Hollitt from the School of Engineering and
Computer Science at Victoria University.

“Back then
there were only 800 data points to use; now we have 41,000
so we are able to map for the first time the magnetic field
of the Milky Way in detail like we've not seen before,”
says Dr Johnston-Hollitt.

The Senior Lecturer in
Victoria’s School of Chemical and Physical Sciences says
there has been a renaissance in radio astronomy in recent
years.

“The map shows the rapid advance of radio
telescopes that work in a different way to optical
telescopes.

“You can’t directly ‘see’ other
galaxies by looking through a radio telescope but we can use
computers to translate radio waves into images. There are
parts of space where a radio telescope will allow us to
‘see’ further than optical telescopes.”

In making
the new map, the research team measured the light from
background galaxies and how the light changes as it passes
through the Milky Way to produce a 3D view of the
galaxy.

In particular, the researchers were able to use
the light that is affected by the galaxy’s magnetic
fields—polarised light—to map the galaxy’s structure.
This technique is known as the Faraday Rotation.

“The
Milky Way is hard to map because we are sitting on the edge
of the galaxy looking through it However, we know that
spiral galaxies like the Milky Way have magnetic fields that
follow a particular pattern so we were able use polarised
light to map the magnetic fields.”

Dr Johnston-Hollitt
says that having many data sources helped create such an
accurate map.

The new, high-precision map not only shows
the structure of the galaxy’s magnetic field on a large
scale, it also reveals small-scale features that help
scientists better understand other aspects such as
turbulence in galactic
gas.

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